It's not gear related. My 41 warrior has most of the gear obtainable from every instance, and he still takes a great pounding from trash mobs. Bosses are not a problem, however tanking 3+ trash mobs makes my healer spam like crazy at times. CC is the best option if you have it, I notice a great ease when mobs are slept and we can focus them down 1by1. So use them CC's and pop them cool downs.